1. Field of Invention
The invention relates to a control device and a control method, and, in particular, to a control device and a control method of a motor.
2. Related Art
A Hall element can sense a position of a magnetic pole of a motor. Thus, the Hall element can be properly disposed in a motor control device to monitor the rotation of the motor.
As shown in FIGS. 1 and 2, a Hall element 11 is disposed at a position P1 to sense changes of a magnetic pole of a DC brushless motor 12 when the motor 12 rotates, and a controller 13 modifies a driving current 121 for driving the DC brushless motor 12 according to a sensing result of the Hall element 11.
However, when the rotating speed of the DC brushless motor 12 increases and if the Hall element 11 is still placed at the position P1, the driving current 121 may have a surge (FIG. 2) near a reverse point, and the phase of the driving current 121 also lags behind the driving voltage of the DC brushless motor 12. Thus, the motor generates the noise during operation and the motor may operate with a poor efficiency. Consequently, the Hall element 11 may be placed at a position P2 according to another prior art. In this case, the phase difference between the driving current 121 and the driving voltage and the condition of generating the surge easily near the reverse point of the driving current 121 can be improved when the DC brushless motor 12 is operating at a high speed. Thus, the noise of the DC brushless motor 12 can be decreased and the operating efficiency can be enhanced. However, the DC brushless motor 12 operating at a low speed may have poor efficiency and louder noise. Consequently, when the DC brushless motor 12 is operating at different rotating speeds, the position P1, the position P2 or any other optimum placing position, where the Hall element 11 is placed, corresponding to other rotating speeds may influence the efficiency of the controller 13 for controlling the DC brushless motor 12.
Thus, it is an important subject of the invention to provide a device and a method for controlling a motor, which are free from being influenced by a placing position of a sensor while the rotating speed of the motor changes. Furthermore, when the rotating speed of the motor changes, the device and method for controlling the motor can response with the rotating speed to generate a proper motor driving current so as to enhance the working efficiency, lengthen the lifetime of the motor and reduce the noise of the operating motor.